1. Field of the Invention
The present invention relates to a communication apparatus and a method of controlling the same.
2. Description of the Related Art
Establishment of the HDMI 1.4 (High-Definition Multimedia Interface Specification Version 1.4) standards enables to communicate Ethernet data via one HDMI cable in addition to video data and audio data. According to the HDMI 1.4, video data and audio data are transmitted from a source device to a sink device using a TMDS (Transition Minimized Differential Signaling) line. As for Ethernet data, two-way communication is performed between a source device and a sink device using an existing HPD (Hot Plug Detect) line and a Utility line that is conventionally Reserved. This allows communication of Ethernet data between HDMI devices without using an Ethernet cable and therefore facilitates network building. An HDMI device joining a network needs to relay Ethernet data between other devices connected to itself.
In general, an HDMI device can transit to a standby state to reduce power consumption in an idle state. In the standby state, power supply to most circuits of the HDMI device stops to reduce power consumption. However, power supply to some circuits (for example, a circuit that receives a signal from a remote controller) continues. In particular, an HDMI device joining a network needs to relay Ethernet data between other devices, as described above, and therefore needs to continuously supply power to the routing circuit (Ethernet switch) even in the standby state. This causes an increase in the power consumption of the HDMI device.
Meanwhile, the other devices connected to the HDMI device joining the network do not necessarily support Ethernet data communication. For example, an HDD recorder connected to a digital television (DTV) complying with HDMI 1.4 may support only HDMI 1.3a but not Ethernet data communication. In this case, even when the DTV continuously supplies power to the Ethernet switch in the standby state, the Ethernet switch is not used at all, and the power is wasted. Even in a state other than standby, power is wastefully supplied to the Ethernet communication unit for an HDMI connector connected to an HEC-incompliant HDD recorder.
For example, Japanese Patent Laid-Open No. 2003-87296 is conventionally known as a technique of reducing the stand-by power consumption of a network device. A network device according to the prior art determines by monitoring a link pulse or the presence/absence of traffic whether an external communication device is connected. If no device is connected, the network device transits to a power saving mode (a state in which only the connection presence/absence detection unit is ON).
However, when the prior art is applied to an HEC-compliant HDMI device (communication apparatus), power may be supplied to the Ethernet switch even if an HDMI device connected to the HDMI connector is HEC-incompliant. This impairs efficient control according to the HDMI standards.